Using a light bulb as a non-linear element in a circuit dates back at least to Western Electric and its 1915-era Panel switch: http://en.wikipedia.org/wiki/Pane

Using a light bulb as a non-linear element in a circuit dates back at least to Western Electric and its 1915-era Panel switch: http://en.wikipedia.org/wiki/Panel_switch http://en.wikipedia.org/wiki/Panel_switch (By the way, if you're near Seattle, interested in electronics and history, and can spare a Tuesday morning, you might enjoy going to visit the Museum of Communications in Georgetown: http://www.museumofcommunications.org/ http://www.museumofcommunications.org/ . I volunteer there when school's not in session.)